[Stem from the Sailors GrammarChap 2 {17C how to book}] The Keel: The first and lowest Timber in a fhip is the Keel, to which is fafstened all the reft; this a great tree or more, hewn to the proportion of her burden, laid by a right line in the bottom of the Docks or Stocks. At one end is Skarfed into the Stem, which is a great timber wrought compaffing, and all the butt-ends of the planks forwards are fixed to it. The Stern poft is another great Timber, which is let into the Keel at the other end fomewhat sloping, ......

From Nate on Mon 3 Apr 2006, 4:25 pm | LinkStem piece: “Nautical The curved upright beam at the fore of a vessel into which the hull timbers are scarfed to form the prow.”

It would be the part of the ship that, on the water line, cuts into the water. It’s usually not really vertical but “raked”. It’s the most forward part of the ship, then, that’s not not used for rigging a sail such as the jib.

More on Stem: meaning in general, main piece derived from 'Sta' Latin to stand via the Germanic type lingos.[ Trunk of Tree or other stalk items }OED:- stem, n.2

OED OTeut. *stamni-z; a parallel and synonymous OTeut. formation (*stamno-z) is represented by (M)LG., (M)Du., OHG., MHG. stam (mod.G. stamm) masc., trunk or stem of a tree (so Sw. stam, Da. stamme, from German); also by OS. stamn (? masc.), ON. stamn, stafn neut., which are recorded only in the derived sense = STEM n.2 The word is Stem n21. The timber at either extremity of a vessel, to which the ends of the side-planks were fastened; the ‘stem’ (in the modern sense) or the stern-post. Hence, either extremity of a vessel, the prow or the stern. Obs.

1601 HOLLAND Pliny VII. lvi. I. 190 Piseus the Tyrrhene..armed the stemme and beake~head of the ship with sharpe tines and pikes of brasse.

1627 CAPT. SMITH Sea Gram. ii. 2 At the one end is skarfed into it the Stem, which is a great timber wrought compassing. Ibid. ix. 53 If her stem be too flat..fix another stem before it, and that is called a false stem, which will make her rid more way and beare a better saile.

1652 NEDHAM tr. Selden's Mare Cl. 54 As far as Nereus doth, to Ashur's Land Plow out a passage with his stemm's and oars.

b. Phrases. from stem to stern (from post to stem): along the whole length of a ship. to give (a ship) the stem: to ram. stem for stem: (of ships) abreast, exactly alongside each other. stem on: so as to strike with the stem. stem to stem: (of ships) with their stems facing each other.